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Home >> Mitsubishi >> 1993 >> Eclipse Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> Code 12: Airflow Sensor
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Code 12: Airflow Sensor

NOTE: For component terminal identification, see TERMINAL IDENTIFICATION  . For wiring diagrams, see WIRING DIAGRAMS article in this section.
NOTE: Procedures are provided by manufacturer for component testing using an engine analyzer with oscilloscope capability. Refer to manufacturer's operation manual for instructions in use of oscilloscope. If using a scan tester, go to step 3.
  1. If using scan tester, go to step 3. Disconnect Airflow Sensor (AFS) connector. Install Test Harness (MB991348 ) between AFS and AFS connector. Using engine analyzer with oscilloscope capability, connect special patterns probe to AFS connector terminal No. 3.
  2. Start engine. Verify that wave form high frequency and low frequency patterns are of approximately the same length (time). See Fig 1 . Verify that wave length decreases and frequency increases as engine RPM increases. If conditions are not as specified, replace AFS. If conditions are as specified, go to step 4.
    Fig 1: Known-Good Airflow Sensor Wave Pattern ID
    G93I80273Courtesy of MITSUBISHI MOTOR SALES OF AMERICA
  3. Warm vehicle to normal operating temperature. Ensure headlights and accessories are off. Ensure steering wheel is in straight-ahead position. Using scan tester, read Airflow Sensor (AFS) volume (frequency) value. See AIRFLOW SENSOR VALUES  table. Frequency should increase when engine is raced. If values are not as specified, replace AFS. If values are as specified, go to next step.
    AIRFLOW SENSOR VALUES

    Application Hz @ 700 RPM Hz @ 2000 RPM
    1.8L 25-40 67-88
    2.0L
    Eclipse
    Non-Turbo 25-50 70-90
    Turbo 25-50 60-85
    Galant 18-44 64-104
  4. On Eclipse, go to step 8. On Galant, disconnect AFS connector and MPI relay connector. Using DVOM, check for continuity between specified AFS connector terminal and MPI relay connector terminal. See AFS TO MPI TERMINAL WIRING HARNESS ID  table. If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
    AFS TO MPI TERMINAL WIRING HARNESS ID

    Application AFS Terminal No. MPI Terminal No.
    Galant 2 3
    Eclipse 4 3
  5. Using DVOM, check for continuity between chassis ground and AFS connector terminal No. 5 (terminal No. 4 on Galant). If continuity does not exist, repair wiring harness as necessary. If continuity exists, go to next step.
  6. Disconnect AFS connector and ECM connector. Using DVOM, check for continuity between specified AFS connector terminal and ECM connector terminal. See AFS TO ECM WIRING HARNESS TERMINAL ID  table. If continuity does not exist on specified circuit(s), repair appropriate circuit for open or short to ground as necessary. If continuity exists, go to next step.
    AFS TO ECM WIRING HARNESS TERMINAL ID

    Application AFS Terminal No. ECM Terminal No.
    Galant 1 70
    7 57
    Eclipse 3 70
    7 19
  7. Turn ignition switch to ON position. Using DVOM, check voltage between chassis ground and AFS harness connector terminal No. 1 on Galant or terminal No. 3 on Eclipse. If voltage is not 4.8-5.2 volts, replace ECM. If voltage is as specified, condition required to set fault is not present at this time. Test is complete. Intermittent problem may exist. See TESTS W/O CODES article in this section.
  8. Disconnect AFS connector. Turn ignition switch to ON position. Using DVOM, check voltage between specified terminal and chassis ground. See AFS CONNECTOR POWER SUPPLY CIRCUIT ID  table. If system voltage does not exist, repair wiring harness as necessary. If system voltage exists, go to next step.
    AFS CONNECTOR POWER SUPPLY CIRCUIT ID

    Application Terminal No.
    Eclipse
    1.8L & 2.0L Turbo 2
    2.0L Non-Turbo 1
  9. With ignition switch in ON position, use DVOM to check voltage between specified terminal and chassis ground. See AFS CONNECTOR VOLTAGE CIRCUIT ID  table. If voltage is not 4.8-5.2 volts, repair wiring harness as necessary. If voltage is as specified, go to next step.
    AFS CONNECTOR VOLTAGE CIRCUIT ID

    Application Terminal No.
    Eclipse
    1.8L 1
    2.0L Non-Turbo 2
    Galant 3
  10. Using DVOM, check for continuity between specified AFS connector terminal and chassis ground. See AFS CONNECTOR GROUND CIRCUIT ID  table. If continuity does not exist, repair wiring harness as necessary. If continuity exists on Eclipse 1.8L or 2.0L non-turbo, condition required to set fault is not present at this time. Test is complete. Intermittent problem may exist. See TESTS W/O CODES article in this section. On all other models, go to next step.
    AFS CONNECTOR GROUND CIRCUIT ID

    Application Terminal No.
    Eclipse
    1.8L & 2.0L Non-Turbo 4
    2.0L Turbo 6
    Galant 5
  11. Disconnect AFS connector and ECM connector. Using DVOM, check for continuity between specified AFS connector terminal and ECM connector terminal. See ECM TO AFS WIRING HARNESS TERMINAL  table. If continuity does not exist on specified circuit(s), repair appropriate circuit for open or short to ground as necessary. If continuity exists, condition required to set fault is not present at this time. Test is complete. Intermittent problem may exist. See TESTS W/O CODES article in this section.
    ECM TO AFS WIRING HARNESS TERMINAL

    Application ECM Terminal No. AFS Terminal No.
    Eclipse 2.0L Turbo 6 1
    All Other Models 57 7
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